Wire line core barrel apparatus



Aug. 19,1969 K -CA'SPER ET AL 3,461,981

WIRE LINE CORE BARRELZAPXARATUS I y 2 Sheets-Sheet 1 Filed April 30, 1968 N. MNHN.

Aug.19,1969 RMASPER'ETAL v3,461,981

WIRE LINE CORE BARREL APPARATUS l Filed April 50, 1968 2 Sheets-Sheet 2 2l Fresa 5"- framers UnitedStates Patent Office Patented Aug. 19, 1969 WIRE LINRCQRE BARR ,L APPARATUS Ray K. Casper and Albert L'.,Linn', Minneapolis, Minn., ass'ignors to E. J. Lon`gy`ear Company, Minneapolis, Minn., a 4corporation 'of Delaware Filed Apr. 30, 1968, Ser. No. 725,399 Int. Cl. E21b 9/20, 25/00 U.S. Cl. 175-246 7 Claims ABSTRACT or THE DISCLOSURE Background of the invention Core barrelapparatus having an outer tube, a ,core barrel inner tube and an axially split third- -tube retained in the inner tubel for facilitating the taking of soft and broken core. In prior art apparatus suchas U.S.` Patents 3,120,282, 3,120,283I and 3,333,647-Whcil uSfc'dlfQr ing cores of soft material or fragmented material there is a problem of removing the drilled core from the innerx tubeu and at the saine time retainingthc parts o f the core` in the relative lpositions as `drilled `from the earth formation. Additionally a problem of a similar nature as that abovementionedA as wellv as other problems are encounteredV in using'structurexs'such as disclosed in'US. Patent 2;O73,'8`76`which.disclosesan outertubefan inner tube andv a non .split third :tube having a major portion thereof located in the inner tiibeln order toY solve'prob'- le'm's of the above mentioned nature aswell. as other problems, this invention has been made.

Summary ofthe invention The invention r is directed to providing an laxially split third tube in a'core' barrel inner tube assembly to facilitate taking samples vof broken and soif-t cores andthe mounting of the third tube ina manner that it maybe readilyremeved from .the innertnbe Other features 0f,v

the invention in elnde the prevfieien ef .readily reielneeeble landingY rings on the core barrel outer tube assembly and the core'barrcl inner tube assembly andgrooyed fluid, by -pass channels in the latchboclyl adjacent the core barrel inner tube assembly landing ring.

In order-that the inventiondescribed hereingmay .be more fully understood,zthenrneaning o f certain terminology as` used in the specificationwill beset forth. -'1he term inner refers to 4that'portionof the drill stern or anelement of an assembly inits 'pdsitiofn for use in ,thedrill stern which is located axially closer-to the bit attached to the drill stem than any other por-tionof the drill stem or elements being referred to, except where the term refers ,to the transverse circumference, or the peripheral surface or the diameter of the drill stem of said elements. The term fouter refers to that portion of the drill stem or. of an element in its -position for use in the drill stem which vis locatedaxially closerfto the mouth of the drillv hole than the other vportion of the drill ste-m or element -being referred to `except .where the term refers to a transverse circumference or the peripheral surface 0r the diameter of an element or the drill stem.

Brief description of the drawings FIGURES l and 2 when arranged one above the other, with the center line' aligned with FIGURE l a-t the top and FIGURE 2 at the bottom, form a composite longitudinal section through the core barrel inner tube assembly and the ldrill stem, said assembly being shown in a latched corereceivingposition. The meeting line between FIG- URE l1(t0p) and FIGURE 2 (below) is at the line A-A;

FIGURE 3 is a somewhat enlarged, transverse cross sectional view generally taken along the line and in the direction of the arrows 3 3 of FIGURE l to illustrate the mounting of the latches;

FIGURE 4 is a somewhat enlarged, transverse cross sectional view, generally taken along'the line and in the direction of the arrows 4-4 of FIGURE 1 to in part illustrate the fluid bypass channels of a core barre-1 inner tube assembly;

,FIGURE 5 is a somewhat enlarged, transverse cross sectional view generally 4taken along the line and in the direction of the arrows 5- 5 of FIGURE 2 to illustrate the upper end portion of the core barrel inner `tube and the structure located therein;

FIGURE `6 is an enlarged, fragmentary transverse crosssectional view generally taken :along the line and in the direction of the arrows 6 6 of FIGURE 2 to illustrate Ithe uid bypass channels adjacent the core lifter case;

FIGURE 47 is anenlarged fragmentary longitudinal view, par-t in cross section, to illustrate the relative positions of the stop ring and the split t-ube liner; and in part of the uid bypass channel adjacent the core lifter case; and

FIGURE 8 is a longitudinal cross sectional View, -part in schematic, illustrating forcing the -split tube liner out of the core barrel inner tube. t

Referring now in particular to FIGURES 1 and 2,

v there is illustrated a hollow drill stern 10 which is made up of sections of pipe coupled together and having an annular drill bit 11 mounted on lthe inner end thereof. Even thoughvthe longitudinal axis of the drill stem as illustrated in FIGURES 1-2 is shown extending in a horizontal direction, it is to be understood that this is for purposes of illustration only; and that, the apparatus of this invention is vfor use not only when the direction of drilling is generally downwardly such that the angle of drilling direction is not inclined from the Vertical in an amount greater than which the core barrel inner tube assembly, generally designated 15, will freefall of the drill stern;l but also -where the latch body release tube and a spear point plug areof a modified construction so that the core barrel inner tubeassembly'is fluidly propellable to the bit end of the drill regardless of the drilling direction such as disclosed in U.S. Patent No. 3,120,282, issued Feb. 4, 1964, U.S. Patent No. 3,120,283, issued Feb, 4, 1964, and U.S. Patent No. 3,333,647, issued Aug. 1, 1967. The portion of the drill stem attached to or extending below pipe section a is commonly referred to as a core barrel outer tube assembly, generally designated 12; the core barrel outer tube assembly being provided for receiving and retaining the core barrel inner tube assembly 15. Details of construction of the core lbarrel outer tube assembly of the general nature used in this invention are set forth in the aforementioned patents, however, as will become more apparent hereinafter, the construction of portions of the assembly 12 is different from that described in one or more of the aforementioned patents. The core barrel outer tube assembly 12 is composed of a core barrel outer tube 18, a reaming shell 19 threadedly connected to the inner end of the tube 18, said shell having hardened material such as diamonds, not shown, on the transverse outer reaming surface and an annular core bit 11 for drilling into the earth formation from which the core sample is taken, said bit being threadedly connected to the inner end of the teaming shell. The outer end of the assembly 12 includes a locking coupling 20 which connects one end of the assembly 12 to 4the adjacent `pipe section 10a of the drill stem. The opposite ends of the coupling 20 is connected to an adapter coupling 21 which is provided with hardened lands 22. The lower end of the locking coupling in conjunction with the annular recess 21a of the adapter coupling forms a latch seat inside the surface of the adapter coupling against which the latches (detents) 16, 17 of the core barrel inner tube assembly are seated for removably retaining the assembly adjacent the core bit. Also, lthe lower end portion of the locking coupling has a projection flange a that extends as a partial cylindrical surface to bear against a face of a latch and cause the latch and other portions of the core barrel inner tube assembly to rotate `with the drill stem when the latches :are in a latch seated position such as indicated in FIGURE 1.

Threadedly connected to the inner end of the adapter coupling is the outer end of the core barrel outer tube 18, the core barrel outer tube having an annular recess 18a to receivingly mount a landing ring 23 in abutting engagement with the adapter coupling (see FIGURE l). As may be noted, the inner diameter of the landing ring is sufficiently smaller than the inner diameter of the remaining portion of the drill stem that is axially outwardly of the core bit to form a suspension shoulder in the core barrel outer tube.

Not previously mentioned is that the reaming shell and the core bit cooperatively provide an -annular recess 11a for seating a stabilizer ring 14 in position to aid in retaining the core barrel inner tube assembly 15 in a centralized condition relative the inner end of the core barrel outer tube assembly. Ring 14 has an annular casing 14a and circumferentially spaced, axially elongated teeth 14hv that extend radially outwardly of the casing. Since the axial length of the casing is less than that of the teeth, there is provided a fluid flow path radially between the casing and the core `bit to permit the majority of drilling uid to bypass the adjacent portion of the core barrel inner tube assembly; while the inner diameter of the casing is slightly larger than the outer diameter of the adjacent part of the core barrel inner tube assembly to permit a small amount of uid bypass between the casing and the core barrel inner tube assembly.

The core barrel inner tube assembly 15 includes a latch body 26 having a pair of detents or latches 16, 17 and a latch insert block mounted thereon, a latch release tube 27 for retracting said latches, an inner tube cap 29 threaded onto the outer end of a core receiving tube 28, and a spindle 30 for connecting the cap to the inner end portion of the latch body for limited relative slidable movement. A bearing 32 is mounted on the spindle in abutting engagement with the inner end of the bearing housing 33 which is also slidably mounted onto the spindle and threadedly connected to cap 29; there being provided a coil spring 34 that at one end abuts against said bearing and at the opposite end against a spring retaining washer 31 which in turn abuts against a nut 35 threaded on the spindle whereby the bearing housing is rotatable and movable :axially a limited amount relative the spindle. The lbearing housing mounts a thrust bearing assembly 36 in abutting engagement with a lirst `rneta'l washer 37. A lock nut 39 is threaded on and pinned through the spindle in abutting engagement with a second metal washer 37, there being provided a pair of resilient shut otf valve washers 38 on the spindle between the rst and second washer 37 arid a third metal washer between the shut olf valve washers 38. A second lock nut 39' is threaded on the spindle in abutting engagement with the inner end of Ithe latch body and to be located axially outwardly of the tirst mentioned lock nut.

The inner end p ortion of the latch body has a plurality of circumferentially spaced, axially elongated grooves to provide teethl2v6a. The axially inner portions of the teeth extend radially youtwardly of the central axis of the core barrel inner tube assembly a shorter distance than the teeth axiallyb outer portions to provide shoulders 2Gb against which the outer axial surface of a landing ring 42 abuts, the landing ring being press fitted on the latch body to movetherewith. As may -be noted from FIGURE 1, the inner diameter of the landing ring 42 is substantially less than the inner diameter of the landing ring 23. Fur ther, the outer diameter of landing ring 42 is substantially greater than the inner diameter of landing ring 23` but substantially less KVthan the outer diameter of landing ring 23. Through the provision of landing rings 23, 42 either one or both can be replaced in the event they become damaged.

Additionally, the inner axial ends of the latch body teeth extendna substantial distance axially inwardly of the landing ring 42. Accordingly, the landing ring 42 in a core barrel inner tube core taking position seats on landing ring .23 for supporting the core receiving tube out of abutting Aengagement with the core barrel outer tube assembly and ,at the same time the grooves in the latch body provide fluid bypass channels to permit fluid to Flow from the annular space between the core barrel inner tube assembly and the core barrel outer tube assembly axially outwardly of rings 23, 42 to the annular clearance space axially inwardly of said rings.

A throughA pin 51 mounts the insert block 25 in the axially elongated latch body slot 26C while a pair of through pins 48 that are mounted in parallel relationship mount the latches 15 and 16 for pivotal movement. To be noted is that the latches 15, 16 are mounted in a common plane in a common slot, the width of the slot 26C in a direction parallel to the pivot axis of pins 48 being only very slightly greater than the corresponding width of a latch. Further, the inward end portions of the latches are rounded to form a close fit with the arcuately curved portions of the insert 25, i.e. the insert having a central portion projecting axially outwardly between the adjacent rounded portions of the latches whereby the latches directly transmit a force from the drill stem to the insert.

The latch release tube 27 is mounted on the outer reduced diameter portion of the latch body that extends outwardly of the latch body teeth for slidable movement between a position abutting against the latch body shoulder 55 and a position axially spaced therefrom. Tube 27 has diametrcally opposed slots 56 through which the outer transverse corner portions of the latches may extend to latchingly engage the latch seat 21a. A torsion spring 57 within the latch body slot resiliently urges the latches t0 pivot about their respective through pin 48 to positions to latchingly engage the latch seat 21a.

An axially elongated slot 58 is formed in the latch body on either side of slot 26e to extend transversely thereto. A through pin 60 is extended through the slots 26C, 58 and and has its opposite ends mountingly retained within opposed apertures in the latch release tube to move therewith. The slots 58 extend axially inwardly sufciently such that when the pin 60` abuts against the inner edges thereof, the pin is located transversely intermediate the latches and the latch release tube abuts against the latch body shoulder 55; and the pin in an axially outer position, the latch release tube is moved sufficiently relative the latch body to retract the latches. Thus, pin 60 limits the movement of the latch release tube outwardly relative the latch body.

A plug 64 has an inner portion extended into the latch release tube, said inner portion being secured to the latch release tube by a pin 66 to prevent movement of the plug relative the release tube. The plug has a spear point 64a extending outwardly beyond the release tube.

The inner end portion of the cap 29 has an axially extending bore 67, bore 67 having an internally threaded inner end portion 67a that threadingly engages the external threads of the inner tube 28. Bore portion 67a opens to a reduced diameter intermediate, threaded bore portion 67b, which in turn opens to the axially outer bore portion 67e. A plurality of transverse bores 68 at their one ends open to bore portion 67e and at their other ends open to the cap exterior surface. Mounted in bore 67 is a check valve that comprises a valve seat member 69 that threadingly extends into bore portion 67h. The valve seat member has an internal bore 70 that has an axially intermediate bore portion 70a that is of progressively smaller diameters in an axially inward direction. An O-ring 71 is mounted in a groove in a portion of the valve seat member that defines bore portion 70a, there being provided a steel ball 72 seatable against the O-ring to prevent fluid ilowing radially inwardly through channel 68 and thence through bore portion 67e to bore portion 67a; but at the same time permitting the ball 72 moving axially outwardly of the `O-ring to permit duid flow through bore 70 from bore portion 67a in a direction toward and to bore portion 67C. Through the provision of this structure a substantially greater volume of fluid may ilow from the inner tube to bores 68 than through a small vent hole in the inner tube, but at the same time prevents lluid ow in the opposite direction.

Slidably mounted in the core barrel inner tube is a plug 74, said plug having an external annular groove that mounts an O-ring 75 for forming a uid seal between the plug and the inner peripheral wall of the inner` tube. The plug has a cylindrical recess 76 that opens toward the valve seat member, the inner diameter ofv said recess being larger than the maximum outer diameter of the valve seat member. A threaded bore 77 is provided in the plug to open to recess 76 and through the surface of the plug axially opposite said recess.

The inner end portion of the plug is of a slightly reduced diameter to provide a shoulder 78, the outer end of the third tube (tube liner) 80, 81 being seated against said shoulder. The third tube is made up of two half sections, each of which in transverse cross section extendsV through an arc of 180. The third tube is of very thin material, for example of steel, and is of such a size to lit snugly inside the inner tube 28 when in place. In order to keep the third tube from moving axially out of contact with the plunger 74, there is provided a beveled stop ring y83. The stop ring is mounted in an annular groove or recess 84 formed in the inner peripheral wall of the core lifter case 85, recess 84 having an annular edge substantially coextensive with the inner annular edge of the inner tube when the core lifter case is properly threaded on the inner tube. The stop ring is a hard resilient steel snap ring that is axially split at 83a and has a beveled edge 83]; that in an axially outwardly direction, extends radially inwardly toward the central axis of the core barrel inner tube assembly. Further, the beveled edge is angled at about an equal but opposite angle relative ythe inner beveled edge of the third tube, the beveled edges being radially opposite one another even when the stop ring is moved in the recess `84 a maximum distance axially away from the inner tube. Further, the inner diameter of the stop ring is less than the inner diameter of the third tube when it is in place in the inner tube 28.

Mounted within the core lifter case for limited axial movement between the position illustrated in FIGURE 2 and a position abutting against the stop ring y88 is a core lifter 87, the core lifter case and core lifter 87 having abutting beveled surfaces to limit the maximum movement of the core lifter away from the stop ring to the position shown in FIGURE 2. The maximum inside diameter of the core lifter 87 is the same or slightly less than the inside diameter of the stop ring; while the diameter of the core bit aperture 11b is substantially the same as the maximum inside diameter of the core lifter.

An axially elongated groove 11C is formed in the inner peripheral wall of the bit 11 to have one end thereof opened between the stabilizing ring casing 14a and groove 11a, grooves 11e, 11a being radially opposite the core lifter case when the core barrel inner tube assembly is in a latched seated, core receiving position. A plurality of circumferentially spaced, axially elongated holes 88 at their one ends open to groove 11c and at their opposite ends through the bit face 11d at locations radially outwardly of the bit aperture 11b. Axially between groove 11e and aperture 11b, the core bit and core lifter case (when the core barrel inner tube assembly is in a core receiving position) form a loose slip t one inside the other to provide a restriction to the llow of cooling and ilushing fluid so that the greater portion of said fluid must pass through the holes 88 and out across the face of the bit. A small part of the fluid passes between the core lifter case and bit and outwardly through the aperf ture 11b. The purpose of the above is to direct most of the fluid away from the inner peripheral wall of the bit defining aperture 11b to prevent the fluid washing away the soft areas of the core.

In order to facilitate the removal of the third tube from the inner tube, there is provided a small plug 90 for being threaded in bore 77 of plug 74 to block passage of uid through said bore, and an auxiliary cap 91 to be threaded on the outer axial end of the core receiving tube 28. A line 92 connects the cap 91 to a pump 94 for applying iluid under pressure to the interior of cap 91, there being provided a valve 93 in line 92 for discontinuing the application of lluid under pressure through the line.

The apparatus of this invention having been described, the use thereof will now be set forth. For purposes of facilitating the description and operation of the inner tube assembly 15, it will be assumed that the drill stem is extended into a hole in the earth formation in a generally vertical direction and that the core barrel inner tube assembly is being lowered in the drill stem. At this time the latches are retained in a retracted position by the inner peripheral wall of the drill stem. lf the inner tube assembly is being lowered at a sufliciently high rate of speed, if fluid were trapped in the core barrel inner tube, it would act to compress the shut off valve washers 38 to an extent to block the passage of fluid past said washer. However, the fluid in the inner tube passes through bore 77 and moves the ball 72 relative the valve seat member to permit iluid to flow through bore 70 and axially outwardly through bores 68. That is, in some cases with prior art core barrel inner tube assemblies where only a small vent hole is provided to the core barrel inner tube, the small vent hole does not allow enough fluid to bypass with the result that such an upward pressure was developed (especially in larger diameter models) that the rubber shut olf valves 38 were compressed to such a degree as to be permanently deformed.

As the inner end of the core lifter case moves adjacent to the portion of the bit defining aperture 11b, the latches 15 and 16 are located radially adjacent the latch seat, and are resiliently urged to a latch seating condition by the torsion spring. Further, at this time the core barrel inner tube assembly landing ring 4Z abuts against the core barrel outer tube landing ring 23 to support the core barrel inner tube assembly in the position illustrated in FIGURES l and 2. At this time, there is provided a uid bypass channel that extends from axially adjacent the plug `64, axially along the latch release tube and thence radially inwardly through the latch body grooves to bypass the landing rings 23, 42 and then downwardly in the drill stern to adjacent the stabilizer ring to bypass said stabilizer ring and then through the groove 11C and primary outwardly through holes S8 and partially outwardly through the drill bit aperture 11b as previously described. Now the core drilling operation is started whereby the cutting of core is begun. Because of the shape of the core bit, an even deepening hole is cut with a rod `shaped core being produced. As the drilling continues, the core barrel outer tube and core bit move relative the core whereby the core extends through the core bit aperture 11b and thence in the core lifter case to abut against adjacent surfaces of the core lifter. As the axial length of the core increases, the core lifter case moves relative the core lifter until the core lifter abuts against the stop ring. Thereafter the core lifter case, the core lifter and the stop ring and the core barrel inner tube move together as a unit. Further drilling results in core being received in the third tube 80, 31. The drilling of core results in core moving into the core barrel inner tube and third tube and pushing uid outwardly through bore 77, bore 70 and bores 68. However, ball72 prevents the flow of uid in the opposite direction which, if not blocked, would wash away soft portions of the core.

After core of the desired length has been cut, for example when a high pressure signal is applied at the surface through the provision of the resilient shut off washers 38, the drilling is stopped and the drill stem pulled outwardly a short distance. Pulling of the drill stem outwardly results in the core lifter case moving axially relative the core and the core lifter whereby through the drag of the core lifter and the core, the core lifter is further axially spaced from the stop ring and is transversely compressed to grippingly hold the core and break the core. Now the core barrel inner tube assembly along with the core is retracted by a suitable overshot assembly (not shown).

After the inner tube assembly full of core has been retracted from the hole, the core lifter case 85 is unscrewed from the inner tube 28, and the inner tube is unscrewed from the cap 29. Now the pipe plug 90 is threaded into bore 77 and cap 91 threaded on the outer axial end of the core receiving tube. At this time plugs 90, 74 and the O-ring provide a piston inside the inner tube 28. Upon opening valve 93 to apply fluid under pressure from pump 94 to cap 91, the plug 74 is forced axially toward the inner axial end of the core receiving tube, and as a result of the plug abutting against tube sections `80, 81, the third tube is forced out of the inner tube 28. Once the third tube has been removed from the inner tube, the top half of the third tube can be lifted off, exposing the undisturbed core sample which is supported in place in the other half section of the third tube. Thus, during the time the core is being removed from the inner tube, the third tube retains the core in the condition in which it was drilled.

In addition to being useful for forcing the third tube out of the inner tube, the plunger 74 serves another useful purpose. That is when the third tube is to be inserted into the inner tube, plunger 74 retains the split tube sections in proper relative positions as the third tube is inserted into the inner tube.

What is claimed is:

1. In wire line core barrel apparatus that includes a drill stem having a core bit at one end thereof and a latch seat axially spaced from said core bit, and a core barrel inner tube assembly having a retractable latch that is extendable into said seat, iirst means for mounting said latch for' movement between a retracted posi tion and an extended position, a core barrel inner tube for receiving core, said inner tube having a first end portion and a second end portion, second means for connecting the first end portion to the iirst means, said second means having av fluid passageway venting fluid from within the inner tube, a core lifter case removably mounted on said tube second end portion, said case having an annular recess adjacent the core receiving tube second end portion, and a core lifter mounted in said case, the improvement comprising a plurality of separate axially elongated tube sections mounted in the inner tube to form a clo'se tit therewith, said tubular sections having axially spaced tirst ends and second ends, a plunger slidably mounted in the core receiving tube first end portion for retaining the tubular sections first ends in place in the inner tube, and third means mounted in said recess for retaining the tubular sections second ends in place in said inner tube.

2. The apparatus of claim l further characterized in that said third means comprises an axially split stop ring mounted in said recess, said stop ring having a beveled edge adjacent said tubular sections that is inclined radially away from the core lifter case in an axial direction toward said plunger.

3. The apparatus of claim 2 further characterized in that said stop ring lhas a substantially smaller inside diameter than the inside diameter of the tubular sections in place in the inner tube and a larger outside diameter than the inside diameter of the inner tube.

4. The apparatus ofclaim 2 further characterized in that said lirst means comprises a latch body having axially elongated, circumferentially spaced grooves, a landing ring mounted on the latch body intermediate the opposite axial ends of saidgrooves to move with said latch body, that the drill stem has a recess axially intermediate the latch seat and the core bit, and that there is provided a landing ring mounted in the drill stem recess for bearing against the latch body landing ring to support the core barrel inner tube assembly in the drill stem.

5. In wire line core barrel apparatus that includes a drill stem having a core bit at one end thereof, a latch seat axially spaced from the core bit and an annular recess axially between the latch seat and the core bit, a rst landing ring mounted in said recess and a retractable wire line core barrel inner tube assembly that includes rst means for receiving a core as the core is drilled, a latch body having a plurality of circumferentially spaced, axially elongated grooves to provide fluid bypass channels, a second landing ring mounted on the latch body for movement therewith axially intermediate opposite ends of said grooves to seat on said lirst landing ring, said second landing ring having a larger outside diameter than the inside diameter of the first landing ring, and third means mounted on the latch body for movement between an extended position to latchingly engage the latch seat and a retracted position.

6. The apparatus of claim 5 further characterized in that the latch body has an axially elongated slot opening through transversely opposite surfaces thereof, and that the third means comprises a rst and a second elongated latch each having a first end portion and a second end portion, a first pivot member for pivotally mounting the first latch first end portion and a second pivot member for pivotally mounting the second latch iirst end portion, said pivot members being mounted on the latch body in transversely spaced, parallel relationship and mounting said latches for pivotal movement in a common plane.

7. The apparatus of claim 6 further characterized in that the lirst means comprises an axially elongated core barrel inner tube having a first end portion and a second 8,461,981 9 10 end portion, a core lifter case mounted on the inner tube References Cited rst end portion, said case having an annular recess adjacent said inner tube, a core lifter mounted by said UNITED STATES PATENTS case, an axially elongated third tube in said inner tube, 2,857,138 10/ 1958 Svendsen 175--246 X said third tube including two separate axially elongated 5 3,120,282 2/1964 Pickard 175-247 X tubular sections, a stop ring slidably retained in Said 3,120,283 2/1964 Braun 175-246 case recess for retaining the adjacent ends of the tubular 3,225,845 12/ 1965 Koontz 175--246 X sections in place in said inner tube, and means Slidably 3,333,647 8/ 1967 Karich 175-247 mounted in the inner tube second end portion for retan- 3,340,939 9/ 1967 Lindelof 175--246 ing the adjacent ends of the tubular sections in place in 10 the inner tube. NILE C. BYERS, JR., Primary Examiner 

